Decision support tools should be used

Nov 30 2013

Since the introduction of AIS in 2001, the question of ‘how to use AIS data on board’ is still unclear.

The International Regulations for Preventing Collisions at sea 1972 (COLREGS) have no reference to AIS but only to radar. Consequently, many navigators are under the impression that AIS information should not be used for collision avoidance, US-based Totem ECDIS said.

This attitude is heard from many officers and Masters, possibly coming from wrong interpretation of the rules by some marine schools. Totem has stressed that AIS information should be used for collision avoidance.

Anybody who is familiar with the COLREGS will counter the opposing reasoning above and will immediately quote rule 7(a), which says ‘Every vessel shall use all available means appropriate’ and consequently AIS should be used if available. However, seafarers are not supposed to be legal experts and should not be in a position where interpretations should be applied.

In order to further understand this issue, one must go back to the original guidelines given by IMO on ‘Use of AIS in Collision Avoidance Situations’. These guidelines are part of IMO Resolution A.917 (22), adopted on 29th November 2001. These guidelines, incidentally, are set to be revised by IMO in 2014.

Reading the guidelines, the text is indeed self-explanatory, Totem said. The guidelines state that ‘AIS is an additional source of navigational information’ and further that ‘AIS can assist in tracking it {a detected ship} as a target’.

Combining the above with the COLREGS requirement that the officer of the watch (OOW) should use ‘all available means’, it is a clear indication that IMO intended the AIS to be used to avoid collisions.

However, a word of caution should be included, Totem said - the guidelines also warn that the seafarer should not rely on AIS alone and should not use the AIS as an excuse to slacken his, or her lookout, or responsibility.

This statement agrees fully with COLREGS requirements for good seamanship and proper lookout. Totem stressed that, in interpreting AIS data by ECDIS systems, the good practice is to use the target positions only and not trust the SOG (speed over ground) and COG (course over ground) computed and sent by the target’s AIS transmitter. Those parameters are calculated separately using the Kalman algorithm, as is customary with ARPA systems.


Decision Support

Item 40 of the AIS guidelines state that ‘AIS information may be used to assist in collision avoidance decision making’. Totem ECDIS claimed that it provides unique decision support tools.

Such tools give the OOW the suggested course of action, either the exact course change, or the exact speed change that is advised in order to avoid collision. With the decision support tools, the decision making process becomes more methodical and the right decision is more often taken, the company said.

Totem ECDIS complies with all the above IMO guidelines, in particular with items 40.1, 41 and 43, and is fully compatible with COLREGS. It is important to emphasise that, complying with IMO guidelines, the decision support tools are based on both AIS and ARPA information, the company said.

Decision support tools are already used for other aspects of navigation, notably for grounding avoidance and route planning. The attitude that was initially noticed with some navigators, namely “we know the rules of the road, we don’t need the machine to tell us what to do” is sometimes apparent. But if everybody knows the rules, why are there so many collisions?

The answer is possibly more and better training, better education and better performance monitoring. Totem ECDIS said that it offered, in addition to the above, advanced decision support tools that can improve safety and provide the ability to avoid dangerous situations.

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